So for the current SYSCHK1 dataset, to know how it is doing in regards to the variables, etc take a look at the following parameters in the OPS/MVS Parms screen (=4.1.1)
GLOBALUSED 2471 NUMBER OF GLOBAL VARIABLES IN USE
GLOBALBLOCKSUSED 5030 NUMBER OF GLOBAL VARIABLE BLOCKS IN U
GLOBALFREEAREAS 81 NUMBER OF FREE AREAS IN GLOBAL WORKSP
GLOBALFREE 16398 NUMBER OF FREE GLOBAL VARIABLE BLOCKS
GLOBALALLOC 21428 NUMBER OF ALLOCATED GLOBAL VARIABLE B
GLOBALMAX 30000 MAX NUMBER OF GLOBAL BLOCKS
The GLOBALMAX is what will fit as defined today, and GLOBALALLOC is the highwater mark. Depending on what needs to be added, use the DASD Calculation Charts in the Installing Guide to determine space needed. However, a simpler, unofficial method would be to note the current GLOBAL* variable values, add a variable, etc and see how much the values change. This would give an indication as to whether more space needs to be allocated or not.